Julia Roberts’ mother battling lung cancer?

Julia Roberts' mother is reportedly battling lung cancer. The August: Osage County star - whose half-sister Nancy Motes overdosed and died on February 9, after writing a ''ranting'' note that allegedly claimed the actress ''drove her'' to suicide - has ''suffered an emotional collapse'' following Nancy's death, as she has been secretly caring for Betty Lou Motes at her home in Malibu since doctors found a cancerous tumor on her lung during a routine MRI scan in November. A source told the National Enquirer: ''She was already reeling from her mom's cancer crisis. Now, she's been deeply hurt and stung by all the criticism after Nancy's death and feels she doesn't deserve it. Julia insists that Nancy's death was not a suicide.''

The insider added that the 46-year-old Oscar-nominated actress ''wants to believe that the overdose was accidental, that somehow Nancy expected to be discovered just before she passed away. Julia's been crying her eyes out ever since.'' Julia moved Betty, who had a heart attack and angioplasty in 2009, into her home late last year to look after her when she was diagnosed. The source added: ''Everyone was frantic because Betty has a history of smoking and emphysema."